Robotic surgical system torque transduction sensing

ABSTRACT

A method of verifying torque measurements of a reaction torque transducer of an instrument drive unit includes a controller receiving a verification signal, generating an acceptable range of torques, receiving a torque signal, comparing the torque signal to the acceptable range of torques, and stopping a motor if the torque applied by the motor is outside of the acceptable range of torques. The verification signal is indicative of the current drawn by the motor and the torque signal is indicative of torque applied by the motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application claiming the benefit ofand priority to U.S. patent application Ser. No. 15/579,308, filed onDec. 4, 2017, which is a National Stage Application of PCT ApplicationSerial No. PCT/US2016/037478 under 35 USC § 371 (a), filed Jun. 15,2016, which claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/180,124 filed Jun. 16, 2015, the entiredisclosure of each of which are incorporated by reference herein.

BACKGROUND

Robotic surgical systems have been used in minimally invasive medicalprocedures. During such a medical procedure, the robotic surgical systemis controlled by a surgeon that interfaces with a user interface. Theuser interface allows the surgeon to manipulate an end effector thatacts on a patient. The user interface has an input controller or handlethat is moveable by the surgeon to control the robotic surgical system.

The end effectors of the robotic surgical system are positioned at theend of a surgical instrument that is connected to robotic arms. Each endeffector can be manipulated by an Instrument Drive Unit (IDU). An IDUmay have a drive motor associated with the end effector and beconfigured to move the end effector about a respective axis or toactuate a particular function of the end effector (e.g., approximate,pivot, etc. jaws of the end effector).

Safety systems in the robotic surgical system monitored the drive motorcurrent. If the measured motor current exceeded a preset safetythreshold a fault would be presumed and the motor would be turned off.These systems had limited ability to detect different types of faults asthey did not take into account the actual forces at the motor output.

There is a need for robust instrument drive unit fault detection that iscapable of identifying different types of faults beyond those associatedwith pure high current draw.

SUMMARY

In an aspect of the present disclosure, verifying a torque measurementof a torque transducer of an instrument drive unit may include receivinga verification signal indicative of current drawn by a motor of theinstrument drive unit. An acceptable torque range based on theverification signal may be identified. The torque measurement may becompared with the acceptable torque range. The motor may be stopped ifthe torque measurement is outside the acceptable torque range.

In aspects, the method may include measuring the torque being applied bythe motor with a reaction torque transducer that is electricallyisolated from the motor. The reaction torque transducer may transmit thetorque signal to the controller. The method may also include generatinga fault signal when the torque applied by the motor is outside of theacceptable range of torques. Generating the fault signal may includeproviding feedback to a clinician in the form of audible, visual, orhaptic feedback to the clinician.

In some aspects, a sensor may transmit the verification signal to thecontroller. A sensor may measure current drawn by the motor to generatethe verification signal.

In another aspect of the present disclosure, a control circuit for amotor of an instrument drive unit includes a sensor, a reaction torquetransducer, and a controller. The sensor is configured to detect currentdrawn by the motor and the reaction torque transducer is configured todetect torque applied by the motor. The controller is in communicationwith the sensor and the reaction torque transducer and is configured tocontrol the motor. The controller is configured to compare the detectedcurrent drawn by the motor to the detected torque applied by the motorto verify the detected torque is within an acceptable range of torquevalues for detected current drawn by the motor.

In aspects, the control circuit includes a motor energy source that isin electrical communication with the motor. The motor energy source maybe electrically isolated from the reaction torque transducer. The sensormay be configured to detect current drawn by the motor from the motorenergy source.

In some aspects, the reaction torque transducer is configured to detecta mechanical property induced by torque applied by the motor. Themechanical property may be strain.

In another aspect of the present disclosure, an instrument drive unit ofa robotic surgical system includes a fixed plate, a first motor, a firstreaction torque transducer, a first sensor, and a first controller. Thefirst motor has a first drive shaft and the first reaction torquetransducer is disposed about the first drive shaft to secure the firstmotor to the fixed plate. The first reaction torque transducer isconfigured to detect torque delivered by the first motor. The firstsensor is configured to detect current drawn by the first motor. Thefirst controller is configured to control the first motor. The firstcontroller is in communication with the first sensor and the firstreaction torque transducer. The first controller is configured tocompare the detected current drawn by the first motor to the detectedtorque delivered by the first motor to verify that the detected torqueis within an acceptable range of torque values for the detected currentdrawn by the first motor.

In aspects, the instrument drive unit includes a second motor, a secondreaction torque transducer, and a second sensor. The second motor has asecond drive shaft and the second reaction torque transducer is disposedabout the second drive shaft to secure the second motor to the fixedplate. The second reaction torque transducer is configured to detecttorque delivered by the second motor. The second sensor is configured todetect current drawn by the second motor. The first controller isconfigured to control the second motor. The first controller is incommunication with the second sensor and the second reaction torquetransducer. The first controller is configured to compare the detectedcurrent drawn by the second motor to the detected torque delivered bythe second motor to verify that the detected torque is within anacceptable range of torque values for the detected current drawn by thesecond motor.

In some aspects, the instrument drive unit includes a third motor, athird reaction torque transducer, a third sensor, and a secondcontroller. The third motor has a third drive shaft and the thirdreaction torque transducer is disposed about the third drive shaft tosecure the third motor to the fixed plate. The third reaction torquetransducer is configured to detect torque delivered by the third motor.The third sensor is configured to detect current drawn by the thirdmotor. The second controller is configured to control the third motor.The second controller is in communication with the third sensor and thethird reaction torque transducer. The second controller is configured tocompare the detected current drawn by the third motor to the detectedtorque delivered by the third motor to verify that the detected torqueis within an acceptable range of torque values for the detected currentdrawn by the third motor.

Further details and aspects of exemplary embodiments of the presentdisclosure are described in more detail below with reference to theappended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described hereinbelow withreference to the drawings, which are incorporated in and constitute apart of this specification, wherein:

FIG. 1 is a schematic illustration of a user interface and a roboticsystem;

FIG. 2 is a side, cross-sectional view of an instrument drive unit ofthe robotic system of FIG. 1;

FIG. 3 is a cross-sectional view taken along the section line 3-3 ofFIG. 2;

FIG. 4 is a schematic illustration of a control circuit of theinstrument drive unit of FIG. 2; and

FIG. 5 is a flowchart illustrating a method of controlling theinstrument drive unit of FIG. 1.

DETAILED DESCRIPTION

Embodiments of the present disclosure are now described in detail withreference to the drawings in which like reference numerals designateidentical or corresponding elements in each of the several views. Asused herein, the term “clinician” refers to a doctor, a nurse, or anyother care provider and may include support personnel. Throughout thisdescription, the term “proximal” refers to the portion of the device orcomponent thereof that is closest to the clinician and the term “distal”refers to the portion of the device or component thereof that isfarthest from the clinician.

The present disclosure generally relates to an instrument drive unit(IDU) for a robotic surgical system that includes a torque transducer(e.g., primary sensor) that measures the torque applied by a motor andprovides a torque signal to a controller that drives the motor. The IDUalso includes a secondary sensor that measures an input to the motor toprovide a verification signal to the controller. The controller comparesthe torque signal and the verification signal to ensure the torquetransducer is functioning properly. If the torque signal is outside ofan acceptable range of values for a given verification signal, thecontroller generates a fault signal and/or stops the robotic surgicalsystem.

As detailed herein, the IDU includes a reaction torque transducer as theprimary sensor. However, it is contemplated that the primary sensor maybe an inline torque transducer.

Referring to FIG. 1, a robotic surgical system 1, is shown and includesa robotic system 10, a processing unit 30, and a user interface 40. Therobotic system 10 generally includes linkages 12 and a robot base 18.The linkages 12 moveably support a surgical instrument having an endeffector or tool 20 which is configured to act on tissue. The linkages12 may be in the form of arms each having a plurality of members 13. Amember 13 a of the plurality of members 13 has an end 14 that supportsend effector or tool 20 which is configured to act on tissue. Inaddition, the end 14 of the member 13 a may include an imaging device 16for imaging a surgical site “S”. Each of the plurality of members 13 ofthe linkages 12 may be connected to one another about joints 15. Theuser interface 40 is in communication with robot base 18 through theprocessing unit 30.

The user interface 40 includes a display device 44 which is configuredto display three-dimensional images. The display device 44 displaysthree-dimensional images of the surgical site “S” which may include datacaptured by imaging devices 16 positioned on the end 14 of the member 13a and/or include data captured by imaging devices that are positionedabout the surgical theater (e.g., an imaging device positioned withinthe surgical site “S”, an imaging device positioned adjacent the patient“P”, imaging device 56 positioned at a distal end of an imaging arm 52).The imaging devices (e.g., imaging devices 16, 56) may capture visualimages, infra-red images, ultrasound images, X-ray images, thermalimages, and/or any other known real-time images of the surgical site“S”. The imaging devices transmit captured imaging data to theprocessing unit 30 which creates three-dimensional images of thesurgical site “S” in real-time from the imaging data and transmits thethree-dimensional images to the display device 44 for display.

The user interface 40 also includes input handles 42 which allow aclinician to manipulate the robotic system 10 (e.g., move the linkages12, the ends 14 of the linkages 12, and/or the tools 20). Each of theinput handles 42 is in communication with the processing unit 30 totransmit control signals thereto and to receive feedback signalstherefrom. Each of the input handles 42 may include input devices whichallow the surgeon to manipulate (e.g., clamp, grasp, fire, open, close,rotate, thrust, slice, etc.) the tools 20 supported at the end 14 of themember 13 a.

For a detailed discussion of the construction and operation of a roboticsurgical system 1, reference may be made to U.S. Patent Publication No.2012/0116416, entitled “Medical Workstation,” now U.S. Pat. No.8,828,023.

Referring also to FIGS. 2 and 3, an instrument drive unit (IDU) 60 isdisposed within or supported on the member 13 a adjacent the end 14. TheIDU 60 is operatively associated with a tool 20 coupled to the end 14 tomanipulate the tool 20 in response to tool signals transmitted from theprocessing unit 30. The IDU 60 includes motors 62 which are eachoperably coupled to a respective converter 64 and a respective reactiontorque transducer 68. Each motor 62 rotates a drive shaft 63 thatextends through a primary sensor or reaction torque transducer 68 inresponse to energy supplied to the motor 62. The converter 64 convertsrotation of the drive shaft 63 of the motor 62 to linear movement of adrive rod and/or cable (not shown). The converter 64 may be secured to afixed plate 61 of the IDU 60. The reaction torque transducer 68 measurestorque applied or delivered by the motor 62 to the converter 64 andthus, measures force applied to the tools 20. The reaction torquetransducer 68 is positioned about the drive shaft 63 of the motor 62 andsecures the motor 62 to the fixed plate 61 of the IDU 60.

For a detailed discussion of the construction and operation of thereaction torque transducer 68, reference may be made to InternationalPatent Application No. PCT/US15/14542, filed on Feb. 5, 2015, andentitled “Input Device Assemblies for Robotic Surgical Systems”, nowU.S. Pat. No. 9,987,094, the entire contents of which are incorporatedherein by reference.

With reference to FIGS. 2 and 3, the IDU 60 includes one or more circuitboards 80 that each include a controller 126 which are provided inaccordance with the present disclosure. As detailed below, thecontrollers 126 are detailed in terms of a singular controller 126;however, it will be appreciated that the IDU 60 may have one or morecontrollers 126. The controller 126 is in communication with one or morereaction torque transducers 68. As shown, the controller 126 is incommunication with a reaction torque transducer 68 by a lead 142 andanother reaction torque transducer 68 by a lead 144. Each lead 142, 144carries a torque signal indicative of torque being applied by the motor62 sensed by the respective torque transducer 68 to the controller 126.

While the torque being applied by the motor 62 may be precisely measuredby the reaction torque transducer 68, the torque being applied by themotor 62 can also be calculated from the amount of current drawn by themotor 62. As detailed below, this calculated torque can be used toverify that the measured torque (i.e., torque detected by the reactiontorque transducer 68) is within an acceptable range of values for adetected amount of current drawn by the motor 62. By verifying that thedetected torque is in the acceptable range of values for a detectedamount of current drawn, a fault may be generated and/or the motor 62may be stopped if the detected torque is outside of the acceptable rangeof values for a detected amount of current drawn. It will be understoodthat when the detected torque is outside of the acceptable range ofvalues for a detected amount of current drawn that the reaction torquetransducer 68 may have failed.

Continuing to refer to FIGS. 2 and 3, the IDU 60 includes sensors 152,154 that provide verification signals to the circuit board 80. Thesensors 152, 154 are each associated with a respective motor 62 todetect an amount of current drawn by the respective motor 62. Eachsensor 152, 154 then sends a respective verification signal to thecontroller 126 indicative of the amount of current drawn by therespective motor 62. The controller 126 compares the verification signalto the torque signal to verify that the torque signal is within anacceptable range of values with respect to the verification signal.

It is contemplated that the sensors 152, 154 may detect a torque andgenerate a current from the detected current. In such embodiments, thecontroller compares the current of the verification signal to the torquesignal to verify that the torque signal is within an acceptable range ofvalues with respect to the verification signal.

With reference to FIG. 4, a control circuit 120 compares the torquesignal to the verification signal to verify that the detected torque iswithin an acceptable range of values for the amount current drawn by themotor 62. The control circuit 120 detects the reaction torque of themotor 62 and detects the amount of current drawn by the motor 62 toverify that the detected torque is within an acceptable range of valuesfor the amount of current drawn by the motor 62.

The control circuit 120 includes the motor 62, the reaction torquetransducer 68, a voltage source 121, a filter 122, an amplifier 124, thecontroller 126, and a sensor 152. The reaction torque transducer 68generates a torque signal that is carried by the leads 132 to the filter122. The filter 122 is a low pass filter to remove noise from the torquesignal. The filter 122 transmits the filtered torque signal to theamplifier 124 which transmits the amplified filtered torque signal tothe controller 126. The controller 126 determines the reaction torque ofthe motor 62 from the torque signal.

The controller 126 sends a control signal to control the motor 62 (e.g.,the rotational speed of the motor 62). The controller 126 may send thesignal to the motor 62 or to a motor energy source 69 that suppliesenergy to the motor 62. As the motor 62 draws energy from the motorenergy source 69, the sensor 152 detects the amount of current drawn bythe motor 62 from the motor energy source 69. The sensor 152 generatesthe verification signal which is indicative of the amount of currentdrawn by the motor 62 and sends the verification signal to thecontroller 126.

The controller 126 compares the torque signal from the reaction torquetransducer 68 with the verification signal from the sensor 152. First,the controller 126 generates an acceptable range of values for thetorque being applied by the motor 62 from the verification signal. Forexample, when the verification signal indicates that the motor 62 isdrawing 0.80 amps of current, an acceptable range of values for thetorque being applied by the motor 62 is about 0.20 N-m to about 0.030N-m. It will be understood that as the amount of current drawn by themotor 62 increases, upper and lower limits of the acceptable range ofvalues for the torque being applied by the motor increases. In addition,as the amount of current drawn by the motor 62 increases, the acceptablerange of values can increase. If the torque signal is within theacceptable range of values, the controller 126 continues to send acontrol signal indicative of continued rotation of the motor 62.

When the torque signal is outside of the acceptable range of values, thereaction torque transducer 68 may be malfunctioning and thus, providinginaccurate measurement of the torque being applied by the motor 62, orthe tools 20 may have hit an obstruction. Accordingly, if the torquesignal is outside of the acceptable range of values, the controller 126may generate a fault signal and/or send a control signal to stoprotation of the motor 62. The fault signal may provide visual, audible,or haptic feedback to a clinician interfacing with the user interface 40(FIG. 1).

With reference to FIG. 5, a method 200 of verifying torque measurementsof a primary sensor or reaction torque transducer 68 of an instrumentdrive unit 60 with a sensor 152 is disclosed in accordance with thepresent disclosure. Initially, the controller 126 receives aninstruction signal to rotate the motor 62. In response to theinstruction signal, the controller 126 sends a control signal to themotor 62 to rotate the drive shaft 63.

While the motor 62 is rotating, the motor 62 draws current from themotor energy source 69 (FIG. 4). This current is measured by sensor 152(Step 210). The sensor 152 generates a verification signal indicative ofthe measured current (Step 212) and transmits the verification signal tothe controller 126 (Step 214). In addition, while the motor 62 isrotating, the reaction torque transducer 68 measures torque applied bythe motor 62 (Step 220). The reaction torque transducer 68 generates atorque signal indicative of the measured torque (Step 222) and transmitsthe torque signal to the controller 126 (Step 224).

The controller 126 receives the verification signal (Step 230) andgenerates an acceptable range of torques which may be applied by themotor 62 for the given verification signal (Step 240). As detailedabove, the acceptable range of torques is proportional to current drawnby the motor 62. The controller 126 then receives the torque signal fromthe reaction torque transducer 68 and compares the torque signal to theacceptable range of torques (Step 250). If the torque signal is withinthe acceptable range of torques, the controller 126 continues to send acontrol signal to the motor 62 to rotate the drive shaft 63 (Step 255).In contrast, if the torque signal is outside of the acceptable range oftorques, the controller 126 stops rotation of the motor 62 by sending acontrol signal or ceasing to send a control signal (Step 260). Thecontroller 126 then generates a fault signal indicative of the torqueapplied by the motor 62 being outside of the acceptable range of torquevalues. The fault signal may be audible, visual, haptic, or anycombination thereof to alert a clinician of the fault.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Any combination ofthe above embodiments is also envisioned and is within the scope of theappended claims. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of particularembodiments. Those skilled in the art will envision other modificationswithin the scope of the claims appended hereto.

What is claimed:
 1. A method of verifying torque measurements of torquetransducers of an instrument drive unit of a robotic surgical system,the method comprising: detecting, with a first sensor, a first currentdrawn by a first motor of the instrument drive unit; sending a firstverification signal to a first controller indicative of the firstcurrent drawn by the first motor; detecting a torque delivered by thefirst motor of the instrument drive unit; identifying an acceptablerange of torque values based on the first verification signal sent tothe first controller; comparing the detected first current drawn by thefirst motor to the detected torque delivered by the first motor toverify that the detected torque delivered by the first motor is withinthe acceptable range of torque values based on the first verificationsignal; and stopping the first motor when the detected torque deliveredby the first motor of the instrument drive unit is outside theacceptable range of torque values based on the first verificationsignal.
 2. The method according to claim 1, further comprising measuringthe torque being delivered by the first motor with a reaction torquetransducer that is electrically isolated from the first motor, thereaction torque transducer transmitting a torque signal indicative ofthe torque being delivered by the first motor to the first controllerperforming the comparing.
 3. The method according to claim 1, furthercomprising generating a fault signal when the detected torque is outsideof the acceptable range of torque values.
 4. The method according toclaim 3, wherein generating the fault signal includes providing feedbackto a clinician, the feedback being audible, visual, haptic, or acombination thereof.
 5. The method according to claim 1, furthercomprising generating the verification signal with the first sensor, thefirst sensor transmitting the verification signal to the firstcontroller.
 6. The method according to claim 5, further comprising:detecting, with a second sensor, a second current drawn by a secondmotor of the instrument drive unit; sending a second verification signalto a second controller indicative of the second current drawn by thesecond motor; detecting a torque delivered by the second motor of theinstrument drive unit; identifying an acceptable range of torque valuesbased on the second verification signal sent to the second controller;comparing the detected second current drawn by the second motor to thedetected torque delivered by the second motor to verify that thedetected torque delivered by the second motor is within the acceptablerange of torque values based on the second verification signal; andstopping the second motor when the detected torque delivered by thesecond motor of the instrument drive unit is outside the acceptablerange of torque values based on the second verification signal.
 7. Acontrol circuit for motors of an instrument drive unit of a roboticsurgical system, the control circuit comprising: a first sensorconfigured to detect current drawn by a first motor of the instrumentdrive unit; a first reaction torque transducer configured to detecttorque applied by the first motor; and a first controller incommunication with the first sensor and the first reaction torquetransducer and configured to control the first motor, the firstcontroller configured to: receive a first verification signal that isindicative of the current drawn by the first motor; receive a firsttorque signal from the first reaction torque transducer; identify anacceptable range of torque values based on the first verificationsignal; and compare the detected current drawn by the first motor to thedetected torque delivered by the first motor to verify that the detectedtorque delivered by the first motor is within the acceptable range oftorque values based on the first verification signal.
 8. The controlcircuit according to claim 7, further comprising: a second sensorconfigured to detect current drawn by a second motor of the instrumentdrive unit; a second reaction torque transducer configured to detecttorque applied by the second motor; and a second controller incommunication with the second sensor and the second reaction torquetransducer and configured to control the second motor, the secondcontroller configured to: receive a second verification signal that isindicative of the current drawn by the second motor; receive a secondtorque signal from the second reaction torque transducer; identify anacceptable range of torque values based on the second verificationsignal; and compare the detected current drawn by the second motor tothe detected torque delivered by the second motor to verify that thedetected torque delivered by the second motor is within the acceptablerange of torque values based on the second verification signal.
 9. Thecontrol circuit according to claim 8, further comprising a motor energysource in electrical communication with the each of the motors, themotor energy source electrically isolated from each reaction torquetransducer.
 10. The control circuit according to claim 9, wherein theeach sensor is configured to detect a respective current drawn by eachmotor from the motor energy source.
 11. The control circuit according toclaim 8, wherein each reaction torque transducer is configured to detecta mechanical property induced by torque applied by each respectivemotor.
 12. The control circuit according to claim 11, wherein themechanical property is strain.